The present invention relates to a continuous casting technology, particularly to a method and apparatus for changing the width of a cast piece or strand in continuous casting operation.
Various kinds of variable width casting molds have been recently developed for producing cast pieces having different widths from one charge of a molten metal. Such molds are usually formed of a pair of spaced apart parallel long copper side members and a pair of spaced apart, parallel short copper side members which are movable along the long side members. The long and movable short side members of the mold which are water-cooled defines a cavity having a certain size. The width of the cavity corresponding to a spacing between movable side members may vary depending upon the width of the finished product required.
In the continuous casting operation, a molten metal is gravity poured into the cavity of the mold and partly solidified in the form of shell by being in contact with the water-cooled mold. A cast piece or strand is continuously withdrawn from the bottom of the mold.
When it is desired to change the size or width of the cast piece, the pouring of the molten metal into the mold is stopped; the molten metal as poured into the mold is withdrawn as a cast piece; thereafter one or both of the short side members are moved; a dummy bar corresponding to a changed width is positioned at the bottom of the mold; the molten steel is poured into the mold; and a cast piece with a new and changed width is withdrawn.
Accordingly, it has disadvantages that a casting operation must be stopped completely each time the width of a casting is changed; that it takes a considerable time before the casting operation is resumed; and that the productivity of the continuous casting operation is thus largely lowered.
Many efforts have been made for developing a method and apparatus for changing the width of the cast piece and withdrawing the cast piece without involving discontinuation of cast piece due to the "break-out".
Japanese Patent Publications Nos. 46-39225, 47-25572 and 53-45781 disclose such methods and apparatuses for effectively overcoming the above-mentioned disadvantages which have been encountered in the prior art. According to Japanese Patent Publication No. 46-39225, there are provided a pair of interconnecting upper and lower solid blocks having different widths depending upon the desired width of the cast piece. In order to change the width of the cast piece, the pouring of a molten metal into a mold is stopped. The upper and lower interconnecting blocks which have been combined with each other are inserted into the mold for interconnecting the lower and upper cast piece having different widths. The blocks disclosed herein have disadvantages that they require high cost for fabrication and are cumbersome to handle since they are heavy weighted.
The Japanese Patent Publication No. 47-25572 discloses an improved adjustable width continuous casting mold including upper and lower slidable plate members. According to that invention, the existing adjustable width casting mold and the oscillation mechanism for the same must be replaced, resulting in high cost of installation.
The Japanese Patent Publication No. 53-45781 discloses a method of enlarging the width of a cast piece comprising stopping the pouring of a molten metal into a mold; positioning a supporting plate at the bottom of the mold; and then moving a side wall of the mold. That method can not be performed for decreasing the width of a cast piece. There is a fear that the solidified shell will break since it is selt-erecting and that the "break-out" of the cast piece will occur.
It is therefore an object of the invention to provide a method and apparatus for effectively overcoming the above-mentioned disadvantages which have been encountered in the prior art.
It is another object of the invention to provide a method and apparatus for enlarging and decreasing the width of a cast piece during the continuous casting operation with a minimal labor and time.
It is a further object of the invention to provide a method and apparatus for changing the width of a cast piece without involving leaks of molten metal or breaking out of the cast piece.
It is a further object of the invention to provide an method and apparatus for changing the width of a cast piece with a minimal length of the cast piece to be discorded where different width cast piece are connected each other.